1. Field of the Invention
The present invention relates to a thermal-transfer printer, particularly relates to a thermal-transfer printer having a thermal head.
2. Description of the Related Art
In a conventional art, there is known a structure for supporting a thermal head having a head supporting member for pivoting the thermal head to a side of a platen roller and a thermal printer (thermal-transfer printer) mounted with the supporting structure.
In JP-A-11-058878, there is disclosed a structure of supporting a thermal head having a head pressing spring plate, a thermal head attached to the head pressing spring plate via a head supporting plate, and a head pressing shaft for pivoting the thermal head to a side of a platen roller. According to the structure of supporting a thermal head disclosed in JP-A-11-058878, the head pressing spring plate includes a middle back plate having a tongue piece having spring performance at a center thereof and portions which are liable to bend provided on both sides thereof, and arm portions provided at both end portions of the middle back plate. The arm portion is pivotably supported by a supporting shaft of a frame. Further, the head pressing shaft is configured to pivot the thermal head to the side of the platen roller by pressing the tongue piece of the head pressing spring plate. Further, in JP-A-11-058878, there is not disclosed a mechanism for moving the head pressing shaft to press the head pressing spring plate.
Further, JP-A-5-085012 discloses a thermal head pressing apparatus of a thermal printer configured to arrange a torsion bar having bending portions at both ends thereof at a supporting portion provided at an upper portion of the thermal head and exert a pressing force to the bending portions. In the structure of supporting the thermal head disclosed in JP-A-5-085012, mentioned above, there is configured to pivot the thermal head provided at a front end portion of a leaf spring member to a side of a platen roller while always balancing left and right pressing forces and generating printing pressure to the thermal head. However, JP-A-5-085012 does not disclose a mechanism of pivoting the leaf spring attached with the thermal head to the side of the platen roller.
Further, JP-A-2001-353923 discloses a thermal printer according to an example of a conventional art having a pair of first link members one end of each of which is pivotably supported by a base portion of an apparatus, at other end of each of which, a vicinity of heat generating portion of the thermal head is supported, and a pair of second link members one end of each of which is supported by the base portion and at other end of each of which, the thermal head is supported. According to the thermal printer disclosed in JP-A-2001-353923, mentioned above, the first link member supporting the thermal head is configured to be made to move between an operating position and an escaping position by transmitting a torque of a worm gear fixed to an output shaft of a motor to a worm wheel provided at a surrounding of a pivoting shaft member of the first link member.
FIG. 12 is a top view showing a thermal-transfer printer according to other example of a conventional art. FIG. 13 is a side sectional view of the thermal-transfer printer according to other example of the conventional art shown in FIG. 12. FIG. 14 is a perspective view showing a heating portion and a pressing member of the thermal-transfer printer according to other example of the conventional art shown in FIG. 12. FIG. 15 is a disassembled perspective view of the heating portion and the pressing member of the thermal-transfer printer according to other example of the conventional art shown in FIG. 14. FIG. 16 through FIG. 20 are perspective views for explaining details of the pressing member and a connecting member of the thermal-transfer printer according to other example of the conventional art shown in FIG. 12. First, an explanation will be given of a structure of a thermal-transfer printer 100 according to other example of the conventional art.
As shown by FIG. 12 and FIG. 13, the thermal-transfer printer 100 according to other example of the conventional art includes a main body frame 110, a platen roller 120, a heating portion 130, a pressing member 140, a power transmitting portion 150, an ink cartridge 160, a first carrying roller 170 and a second carrying roller 180. Further, the power transmitting portion 150 includes a motor 151, two middle gears 152, and a drive gear 153. The motor 151 transmits a drive force to the drive gear 153 via the two middle gears 152.
The main body frame 110 is provided with two supporting shafts 111 for pivotably supporting two side faces of the heating portion 130 opposed to each other. A torsional coil spring 111a is mounted to one side of the two supporting shafts 111. The torsional coil spring 111a is mounted to urge to pivot the heating portion 130 in an arrow mark E direction of FIG. 13. Further, as shown by FIG. 13, the heating portion 130 is configured to be pivotable in the arrow mark E direction or an arrow mark F direction of FIG. 13 and pressed to the platen roller 120 by a predetermined pressing force. As shown by FIG. 13 through FIG. 15, the heating portion 130 includes a thermal head 131, a pair of head attaching arms 132, a pair of head supporting arms 133, two compression coil springs 134, a heat radiating member 135.
The thermal head 131 is provided with a function of generating heat to predetermined temperature. Further, as shown by FIG. 15, two spring attaching boss portions 131a are provided at an upper face of the thermal head 131. Further, the pair of head attaching arms 132 include arm a pressing portions 132a, fitting hole portions 132b, and head attaching portions 132c. The arm pressing portion supporting arm 133 urged to pivot in the arrow mark E direction of FIG. 13 relative to the thermal head 131. The fitting hole portion 130b is fit to the supporting shaft 111 of the main body frame 110. Further, the head attaching portion 130c is attached with the thermal head 131.
Further, the pair of head supporting arms 133 are provided to pinch the pair of head attaching arms 132 attached with the thermal head 131 from outer sides. The head supporting arm 133 includes a boss portion 133a, a fitting hole portion 133b, and a spring pressing portion 133c. The boss portion 133a is provided to project to an outer side at a side face of a vicinity of one end portion of the head supporting arms 133. Further, the fitting hole portion 133b is provided at a vicinity of other end portion of the head supporting arm. The fitting hole portion 133b is fit with the supporting shaft 111 of the main body frame 110. Further, the spring pressing portion 133c is provided to project from an upper portion of the head supporting arm 133 to an inner side.
Further, the two compression coil springs 134 are respectively fit between the two spring attaching boss portions 131a of the thermal head 131 and the spring pressing portions 133c of the pair of head supporting arms 133. Thereby, the thermal head 131 is brought into a state of being supported by the head supporting arm 133 via the compression coil spring 134. Further, the heat radiating member 135 is arranged above an upper face of the thermal head 131 and is provided with a function of radiating heat of the thermal head 131.
Further, as shown by FIG. 12 through FIG. 15, the pressing member 140 is configured to be able to move the thermal head 131 to a side of the platen roller 120 by pressing the boss portion 133a of the pair of head supporting arms 133 and transmitting the pressing force to the thermal head 131 via the compression coil springs 134. The pressing member 140 includes a first pressing arm 141, a second pressing arm 142, and a connecting member 143. As shown by FIG. 16 and FIG. 17, the first pressing arm 141 includes a fitting portion 141a in an oval shape. As shown by FIG. 12 and FIG. 17, the fitting portion 141a of the first pressing arm 141 is fit with an oval shape portion 143a of the connecting member 143 from a side opposed to a side for providing the power transmitting portion 150. Further, as shown by FIG. 18, the second pressing arm 142 includes a fitting portion 142a in an oval shape and a gear engaging portion 142b. As shown by FIG. 12 and FIG. 20, the fitting portion 142a of the second pressing arm 142 is fit with an oval shape portion 143c (refer to FIG. 19) of the connecting member 143 on a side provided with the power transmitting portion 150. Further, the gear engaging portion 140b of the second pressing arm 142 is arranged to engage with the drive gear 113 of the power transmitting portion 150.
Further, as shown by FIG. 14 and FIG. 15, the connecting member 143 is formed by a rod-like member. The connecting member 143 is connected with the first pressing arm 141 and the second pressing arm 142. Further, the connecting member 143 is provided with a function of transmitting a drive force provided from the drive gear 153 engaged with the gear engaging portion 142b of the second pressing arm 142 to the first pressing arm 141. As shown by FIG. 19, the connecting member 143 includes a groove portion 143b and the oval shape portion 143c in addition to the above-described oval shape portions 143a. The oval shape portions 143a and 143c are provided on both sides of the connecting member 143 and formed by cutting. Further, as shown by FIG. 12 and FIG. 14, the groove portion 143b is fit with an E ring 144.
FIG. 21 and FIG. 22 are side sectional views for explaining operation of the thermal-transfer printer according to other example of the conventional art. Next, an explanation will be given of operation of the thermal-transfer printer 100 according to other example of the conventional art in reference to FIG. 21 and FIG. 22. As operation of the thermal-transfer printer 100 according to other example of the conventional art, first, by rotating the first carrying roller 170 and the second carrying roller 180 in an arrow mark A direction of FIG. 21, the record sheet 200 is carried to between the attaching roller 120 and the thermal head 131 of the heating portion 130. When the carried record sheet 200 comes to a printing start position, by the drive force transmitted from the power transmitting portion 150 (refer to FIG. 12), the pressing member 140 is pivoted in an arrow mark C direction of FIG. 21. Further, by pivoting the pressing member 140 in the arrow mark C direction of FIG. 21, the boss portions 133a of the pair of head supporting arms 133 of the heating portion 130 are respectively pressed down by the first pressing arm 141 and the second pressing arm 142 of the pressing member 140 (refer to FIG. 12). Thereby, the heating portion 130 is pivoted in an arrow mark F direction by constituting a fulcrum by the supporting shaft 111. Thereby, as shown by FIG. 22, the thermal head 131 heated to predetermined temperature presses the platen roller 120 to pinch the ink sheet 161 of the ink cartridge 160 and the record sheet 200 and therefore, thermally melting ink coated on an ink sheet 161 of the ink cartridge 160 is melted to transfer an image onto the record sheet 200. Thereafter, in accordance with pivoting the pressing member 140 in an arrow mark D direction of FIG. 22, the heating portion 130 urged by the torsional coil spring 111a (refer to FIG. 12) is pivoted in an arrow mark E direction of FIG. 22. Thereby, the pressing force of the thermal head 131 of the heating portion 130 to the platen roller 120 is released. Further, by rotating the first carrying roller 170 and the second carrying roller 180 in an arrow mark B direction of FIG. 22, the record sheet 200 transferred with the image is carried to a discharge side.
However, according to the thermal-transfer printer 100 shown in FIG. 12, the oval shape portions 143a and 143c provided on both sides of the connecting member 143 for connecting the first pressing arm 141 and the second pressing arm 142 are formed by cutting which takes time in working and therefore, there poses a problem that a number of steps of working the connecting members 143 is increased and fabrication cost is increased.
Further, in the thermal-transfer printer 100 shown in FIG. 12, a torque is transmitted from the second pressing arm 142 to the first pressing arm 141 by the oval shape portions 143a and the 143c of the connecting member 143 and therefore, when a larger torque is going to be transmitted from the second pressing arm 142 to the first pressing arm 141, an excessive force is exerted to the fitting portion 141a and the fitting portion 142a of the first pressing arm 141 the second pressing arm 142. Therefore, there also poses a problem that the fitting portion 141a and the fitting portion 142a are liable to be deformed and the first pressing arm 141 and the second pressing arm 142 are liable to be destructed.
Further, in JP-A-11-058878 and JP-A-5-085012, mentioned above, a structure of pressing to pivot a member for supporting the thermal head to a side of the platen roller is not disclosed and therefore, it seems that a structure per se constituting a premise of the invention is not disclosed. Further, also according to the thermal printer disclosed in JP-A-2001-353923, mentioned above, a structure of attaching the worm wheel and the pivoted shaft member is not disclosed and therefore, similar to JP-A-11-058878 and JP-A-5-085012, mentioned above, it seems that a structure per se constituting the premise of the invention is not disclosed.